1. Field of the Invention
The present invention relates to inorganic materials such as cement and slag as well as construction compositions containing cement or slag which are used mainly in constructions or buildings and civil engineering works and to methods for the production of such inorganic materials. The present invention also relates to apparatuses for the production of spheroidal inorganic materials.
2. Description of Related Arts
In forming various constructions or building or civil engineering works, a large amount of inorganic construction materials such as cement, slag or the like have been used. Also, various inorganic compositions for use in civil engineering works or construction, such as those for ground stabilization treatment, for example, ground improvers and solidifiers, and compositions for use as concrete or mortar work materials, for example, admixtures or adjuvants, grout materials, plastering materials and the like have been used.
In order to improve the flowability or filling properties thereof, it has been a common practice to add fly ash, an organic adjuvant or the like upon use. Fly ash, which is obtained mainly as a by-product of steam power stations in the form of fine powder of coal ash or cinders, is somewhat limited not only in amount but also in application because it contains carbon to be burned and has a blackish gray color. Organic adjuvant is expensive and the use thereof increases costs. Furthermore, the organic adjuvant changes only the surface activity of the particles concerned, failing to completely solve the question of improving the flowability and filling properties of the material.
In the case where cement such as Portland cement is to be produced, it has heretofore been the practice that raw materials are pulverized and the resulting suspension is preheated in a suspension preheater, calcined in a rotary kiln and the resulting cement clinker is then cooled rapidly in a cooler with air. The cooled cement clinker is then admixed with gypsum powder and the mixture is pulverized using a tube mill, for example, to obtain cement having a desired particle size. Thus, in the production of cement, the cement clinker is brought into contact with air to rapidly cool it. The clinker obtained as by means of an air quenching cooler includes masses having an average particle diameter of from several cm to several tens of cm, and in order to adjust the particle size of the clinker to a predetermined value, usually a mass having a particle size no smaller than a predetermined value (e.g., several cm or less) must be roughly ground to have a value no larger than a predetermined value. The rough grinding of the cement clinker prior to charging into a tube mill or the like makes the production procedure complicated and makes continuous production difficult. In order to overcome this disadvantage, it has already been proposed that the inside of the tube mill be divided into two rooms, i.e., an anterior room and a posterior room and that rough grinding be conducted in the anterior room and pulverization in the exterior room. While this proposal has solved the problem of continuous production, the procedure is still complicated, and furthermore, the particles obtained are angular or have sharp edges, thus increasing the frictional resistance between the particles, resulting in a situation such that when cement and water are kneaded the cement composition or slurry has somewhat poor flowability and filling properties.
On the other hand, slag is an artificial mixture formed purposely when metals are molten in a furnace, such as smelting by the addition of a flux. Slag is composed mainly of silica (SiO.sub.2) and is utilized for the production of Portland blast furnace cement, bricks, ballast, or gravel and the like. Usually, the particle size of the slag is adjusted to a predetermined value before the slag is used by grinding bulky or sandy slag just after it is discharged from the furnace, using a tube mill or a vertical mill, with a following admixture of gypsum, if desired, and pulverization. Conventional slag has also a problem in that it is in the form of particles which have sharp edges or which are angular and cause frictional resistance between the particles, thus decreasing, more or less, the flowability and filling properties of the slag particles themselves and of compositions to which the slag particles are added.
Furthermore, in the case of quick-hardening cement which includes cement clinker powder containing a quick-hardening component (11CaO.multidot.7Al.sub.2 O.sub.3 .multidot.CaF.sub.2) in an amount of from 1 to 30% by weight based on the total weight of the composition and anhydrous or semi-anhydrous cement as disclosed in Japanese Patent Publications Nos. 39924/1972 and 36491/1978, it is difficult to control the hardening time of the quick-hardening cement. In order to solve this problem, it has hitherto been proposed to add a retarder. However, the addition of a retarder in the quick-hardening cement composition with a view to controlling its hardening time results in a considerable decrease of the final strength of the cement composition. Attempts to control the hardening time by admixing a quick-hardening cement with an ordinary cement (non-quick-hardening cement) in various proportions have led to another problem in that a decrease in strength occurs due to the anhydrous gypsum contained in the ordinary cement. In addition, the ordinary cement has low flowability as described above.
Furthermore, an improvement in the energetic efficiency of the process for the production of such particulate inorganic material has also been desired.